Effect of incorporation of microstructured carbonized cellulose on surface and mechanical properties of epoxy composites

Recent Advances in Biochar Polymer Composites

“Biochar” (BC) is the solid residue recovered from the thermal cracking of biomasses in an oxygen-poor atmosphere. Recently, BC has been increasingly explored as a sustainable, inexpensive, and viable alternative to traditional carbonaceous fillers for the development of polymer-based composites. In fact, BC exhibits high thermal stability, high surface area, and electrical conductivity; moreover, its main properties can be properly tuned by controlling the conditions of the production process. Due to its intriguing characteristics, BC is currently in competition with high-performing fillers in the formulation of multi-functional polymer-based composites, inducing both high mechanical and electrical properties. Moreover, BC can be derived from a huge variety of biomass sources, including post-consumer agricultural wastes, hence providing an interesting opportunity toward a “zero waste” circular bioeconomy. This work aims at providing a comprehensive overview of the main achievements obtained by combining BC with several thermoplastic and thermosetting matrices. In particular, the effect of the introduction of BC on the overall performance of different polymer matrices will be critically reviewed, highlighting the influence of differently synthesized BC on the final performance and behavior of the resulting composites. Lastly, a comparative perspective on BC with other carbonaceous fillers will be also provided.

Adsorption-enhanced photocatalytic property of Ag-doped biochar/g-C3N4/TiO2 composite by incorporating cotton-based biochar

In this study, the biochar obtained from waste cotton fibers was introduced into the Ag-doped g-C3N4/TiO2 hybrid composite through a facile one-step hydrothermal process. The morphology, elemental composition, crystal structure, microstructure, specific surface area, chemical bonding state, energy band structure, and separation efficiency of photoinduced charge carriers of the resultant composite were examined using scanning electron microscope, energy dispersive X-ray spectrometer, X-ray diffractometer, transmission electron microscope, surface area analyzer, X-ray photoelectron spectroscope, Ultraviolet-visible spectrophotometer, ultraviolet photoelectron spectroscope, and photoluminescence spectroscope. The adsorption isotherms, kinetics and thermodynamics of the biochar, Ag-doped g-C3N4/TiO2 and Ag-doped biochar/g-C3N4/TiO2 were evaluated using the model methyl orange dye. The photoacatalytic degradation of the model pollutants including methyl orange, methylene blue, congo red, and tetracycline hydrochloride and the photocatalytic reduction of Cr(VI) ions were also assessed under visible light. Experimental results indicated that the photocatalytic property of the Ag-doped biochar/g-C3N4/TiO2 was significantly enhanced through the adsorption enhancement compared with the Ag-doped g-C3N4/TiO2. This was due to the uniform doping of multi-scale porous biochar with g-C3N4 nanosheet, Ag and TiO2 nanoparticles. The adsorptive enhancement induced by the biochar resulted in the narrowed band gap, suitable electronic energy band structure, and fast separation of photoinduced charge carriers of the Ag-doped biochar/g-C3N4/TiO2, which was probably due to the coexistence of multi-valence Ti+4/+3 and Ag0/+1 species and oxygen-containing groups of biochar. The major reactive species of the Ag-doped biochar/g-C3N4/TiO2 were 1O2 and h+. The MO dye adsorption onto the Ag-doped biochar/g-C3N4/TiO2 followed the Langmuir isotherm model, pseudo-first-order and pseudo-second-order kinetic models, and the adsorption process was an endothermic reaction with entropy reduction effects. As such, the Ag-doped biochar/g-C3N4/TiO2 exhibited a promising application for the treatment of wastewater containing multi-pollutants especially organic dyes and heavy metal ions.

Damage Management of Concrete Structures with Engineered Cementitious Materials and Natural Fibers: A Review of Potential Uses

The importance of the safety and sustainability of structures has attracted more attention to the development of smart materials. The presence of small cracks (<300 µm in width) in concrete is approximately inevitable. These cracks surely damage the functionality of structures, increase their degradation, and decrease their sustainability and service life. Self-sensing cement-based materials have been widely assessed in recent decades. Engineers can apply piezoresistivity for structural health monitoring that provides timely monitoring of structures, such as damage detection and reliability analysis, which consequently guarantees the service life with low maintenance costs. However, concrete piezoresistivity is limited to compressive stress sensing due to the brittleness of concrete. In contrast, engineered cementitious composites (ECC) present excellent tensile ductility and deformation capabilities, making them able to sense tensile stress/strain. Therefore, in this paper, first, the ability of ECC to partly replace transverse reinforcements and enhance the joint shear resistance, the energy absorption capacity, and the cracking response of concrete structures in seismic areas is reviewed. Then, the potential use of natural fibers and cellulose nanofibers in cementitious materials is investigated. Moreover, steel and carbon fibers and carbon black, carbon nanotubes, and graphene, all added as conductive fillers, are also presented. Finally, among the conductive carbonaceous materials, biochar, the solid residue of biomass waste pyrolysis, was recently investigated to improve the mechanical properties, internal curing, and CO2 capture of concrete and for the preparation of self-sensing ECC.

Innovative Biochar-Based Composite Fibres from Recycled Material

Carbon materials are becoming crucial in several industrial sectors. The drawbacks of these materials include their high cost and oil-based essence. In recent years, recycled materials have become possible alternative sources of carbon with several advantages. Firstly, the production of this alternative source of carbon may help to reduce biomass disposal, and secondly, it contributes to CO₂ sequestration. The use of carbon derived from recycled materials by a pyrolysis treatment is called biochar. Here, we present composite materials based on different biochar filler contents dispersed in several thermoplastic polymer matrixes. Electrical conductivity and tensile break strength were investigated together with the material characterisation by DTA/TGA, XRD, and scanning electron microscopy (SEM) imaging. Materials with good flexibility and electrical conductivity were obtained. The local ordering in composites resembles both biochar and polymer ordering. The similarity between biochar and carbon nanotubes’ (CNTs) XRD patterns may be observed. As biochar is highly cost-effective, the proposed composites could become a valid substitute for CNT composites in various applications.

Biocomposites from Organic Solid Wastes Derived Biochars: A Review

The replacement of natural fiber with biochars to prepare biocomposites has attracted widespread attention recently. Biochar has unique properties, including the porous structure, large specific surface area, high thermal stability, good conductivity, renewable and abundant feedstock source, and environmental friendliness, which provide excellent properties, environmental benefits, and low production costs for biochar-based composites. Biocomposites from organic solid waste-derived biochars show good prospects worldwide in terms of positive social, environmental, and economic impacts. This paper reviews current biochars, elucidates the effects of biochars on the characteristics and performance of biochar composites, and points out the challenges and future development prospects of biochar composites.